How can I write to a file from a livecycle designed PDF?

[Former Community Member]

I am producing a PDF in Livecycle designer and would like to write a sub-set of data from the document.

I have tried methods such as exportData() but this exports everything which i don't need.

I have seen another method which is to attach a file and write to that but ideally I'd just like to be able to create a new file.

var data = xfa.data.nodes.item(0).nodes.item(1).saveXML()  
var oFile = util.streamFromString(data , "utf-8");

I would like to write oFile.

Thanks in advance

Edit:

I would like to add that ideally the user would be presented with a save as dialog  box, so the can choose the location of where to save the xml data.